Something i have noticed recently is a slight sqeal coming from, i think, the rear passenger side drum brake. This is just driving along slowly, no use of the brake.

Is this likely? Should i be concerned, anything to watch out for?

You've got a GLX. Are you sure the rear brakes are drums?

Also, does the noise go away sometimes:-

1) Randomly, and come back equally randomly, and/or

2) When you brake?

having seen the rusty mess hidden by the rear wheels if they are discs i have a serious problem!

Definitely drums,

I only notice it when i start off in the morning or after the car has been sitting, it is only if quite, any speed and the noise, if it is happening, is inaudible. Never very loud. Just wondering if something is binding a little when warm and/or something might be a bit sticky and not fully releasing,

Just checking they were drums. It sounds like your hb mechanism might be sticking on slightly on one side until it gets knocked off properly. I'd try lubricating the external pivots etc, and if it's not cured in a week or so, then think about taking the drums off and cleaning brake dust out of them.